Major types of mutation and their distinguishing features (Table 14.1 in your book)
Basis of Classification
Origin
Major Types of Mutations
Spontaneous
Induced
Cell type
Somatic
Expression
Germ-line
Conditional
Unconditional
Effect on Function
Molecular change in DNA
sequence
Loss-of-function
(also called knockout, or
null)
Hypomorphic (leaky)
Hypermorphic
Gain-of-function (also
called ectopic expression)
Nucleotide substitution
Transition
Transversion
Insertion
Deletion
Effect on Translation
Synonymous (silent)
Missense (Nonsynonymous)
Nonsense (termination)
Frameshift
Major features
Occurs in absence of known
mutagen
Occurs in presence of
known mutagen
Occurs in nonreproductive
cells
Occurs in reproductive cells
Expressed only under
restrictive conditions (such
as high or low temperature)
Expressed under any
conditions
Eliminates normal function
Reduces normal function
Increases normal function
Expressed at incorrect time
or in inappropriate cell
types
One base pair in duplex
DNA replaced with a
different base pair
Pyrimidine (T or C) to
pyrimidine,
or Purine (A or G) to purine
Pyrimidine (T or C) to
purine (A or G)
Or Purine (A or G) to
pyrimidine (T or C)
One or more extra
nucleotides present
One or more missing
nucleotides
No change in amino acid
encoded
Change in amino acid
encoded
Creates translational
termination codon (UAA,
UAG, or UGA
Shifts triplet reading of
codons out of correct phase
The Genetic Code (DNA)
TTT Phe
TCT Ser TAT Tyr
TGT Cys
TTC Phe
TCC Ser TAC Tyr
TGC Cys
TTA Leu
TCA Ser TAA STOP TGA STOP
TTG Leu
TCG Ser TAG STOP TGG Trp
CTT Leu
CCT Pro CAT His
CGT Arg
CTC Leu
CCC Pro CAC His
CGC Arg
CTA Leu
CCA Pro CAA Gln
CGA Arg
CTG Leu
CCG Pro CAG Gln
CGG Arg
ATT Ile
ACT Thr AAT Asn
AGT Ser
ATC Ile
ACC Thr AAC Asn
AGC Ser
ATA Ile
ACA Thr AAA Lys
AGA Arg
ATG Met* ACG Thr AAG Lys
AGG Arg
GTT Val
GCT Ala GAT Asp
GGT Gly
GTC Val
GCC Ala GAC Asp
GGC Gly
GTA Val
GCA Ala GAA Glu
GGA Gly
GTG Val
GCG Ala GAG Glu
GGG Gly
*When within gene; at beginning of gene, ATG signals start of translation.